Wide‐Compatibility Gene S5n Exploited by Functional Molecular Markers and Its Effect on Fertility of Intersubspecific Rice Hybrids

Abstract

ABSTRACTEmbryo‐sac abortion is one of the most important reasons for hybrid sterility between indica and japonica subspecies. Wide compatibility gene S5n can overcome the embryo‐sac sterility between indica–japonica hybrids caused by the S5 locus located on chromosome 6. In this paper, key sequence analysis and functional molecular markers were used to identify S5n gene–harboring genotypes from 646 rice (Oryza sativa L.) genotypes, including 323 cultivated and 323 wild rice genotypes. Whole‐mount eosin B–staining confocal laser scanning microscopy was employed to observe the embryo‐sac fertility of hybrids. A total of 28 genotypes, including 16 cultivated, 9 Oryza rufipogon accessions, and 3 Oryza nivara accessions, were found to have the S5n gene. These results suggested that the S5n gene differentiated and evolved from wild rice. Different indica–japonica hybrids were developed using O. sativa genotypes carrying the S5n gene and without the S5n gene. Embryo‐sac fertility was more than 93% in the S5n gene–harboring hybrids, whereas embryo‐sac fertility was relatively low in control hybrids between typical indica and japonica cultivars without the S5n gene, suggesting that S5n can overcome the sterility between indica–japonica hybrids. Furthermore, it verified the reliability of molecular functional markers to detect S5n gene–harboring genotypes. Functional molecular markers used in the present study will be very useful to identify S5n gene–harboring genotypes, and genotypes detected with the S5n gene in the present study are very important germplasm for overcoming intersubspecific hybrid sterility.